Process for regenerating used lubricating oils

ABSTRACT

A process for regenerating used oils comprising contacting the same with a light paraffinic hydrocarbon as solvent, separating from the resulting mixture a solution of clarified oil and a residue, separating a substantial portion of the solvent from the clarified oil in a first flash zone, separating substantially the rest of the solvent from the clarified oil in a second flash zone, admixing with the residue a viscosity lowering agent, separating a substantial portion of the solvent vapors from the resulting mixture in a third flash zone and further separating substantially the rest of the solvent vapors from said residue in a fourth flash zone, condensing the solvent vapors from the first, second and fourth zones and admixing the resulting condensate with the solvent vapors from the third zone.

United States Patent [191 Vu etal. I

[ PROCESS FOR REGENERATING USED LUBRICATING OILS [75] Inventors: Quang Dang Vu, Paris; Francois Audibert, Lyon; Jean Francois Boucher, Saint Germain en Laye; Henri DeVille, La Celle Saint Cloud, all of France [73] Assignee: Institut Francais du Petrole, des

Carburants et Lubrlfiants, Rueil-Malmaison, France [22] Filed: June 4, 1971 [21] Appl. No.: 150,139

[30] Foreign Application Priority Data June 8, 1970 France 7021053 [52] US. Cl. 208/180, 203/45 [51] Int. Cl... Cl0g 27/100 [58] Field of Search 208/180, 179, 48; 203/43, 45

[56] References Cited UNITED STATES PATENTS 2,655,468 10/1953 Greene 203 45 19,007 6/1932 India 203/180 710,305 5/ 1965 Canada 208/ l 80 Primary Examiner-Delbert E. Gantz Assistant Examiner-Juanita M. Nelson Attorney-Millen, Raptes & White [57 ABSTRACT A process for regenerating used oils comprising contacting the same with a light paraffinic hydrocarbon as solvent, separating from the resulting mixture a solution of clarified oil and a residue, separating a substantial portion of the solvent from the clarified oil in a first flash zone, separating substantially the rest of the solvent from the clarified oil in a second flash zone, admixing with the residue a viscosity lowering agent, separating a substantial portion of the solvent vapors from the resulting mixture in a third flash zone and further separating substantially the rest of the solvent vapors from said residue in a fourth flash zone, eondensing the solvent vapors from the first, second and fourth zones and admixing the resulting condensate with the solvent vapors from the third zone.

. 11 Claims, 1 Drawing Figure PROCESS FOR REGENERATING USED LUBRICATING OILS This invention relates to an improved process for regenerating used lubricating oils.

It is known that several processes for regenerating used lubricating oils are already available. One of the most efficient processes for regenerating used oils is finic hydrocarbons, the oil is generally subjected to one or more finishing treatments, i.e., a treatment with acid, with earth or with hydrogen, before or after a separation of the different cuts, for example, by distillation.

The step of contacting the used oil with the light paraffinic hydrocarbon is generally conducted in a column from which there is withdrawn an overhead a mixture of paraffinic hydrocarbon and at least partially purified oil, thereafter called clarified oil, and a bottom residue containing the said paraffinic hydrocarbon.

From the first mixture there is separated, generally by use of a series of flashes, the paraffinic hydrocarbon from the clarified oil. Said paraffinic hydrocarbon, after cooling, compression and condensation, is generally reused in a new purification step of used oil.

As far as the residual portion is concerned, the difficulty of handling the same due to its siccative character and its high viscosity, has been, upto now, the main impediment to the application of the treatment with propane to used'oils.

in addition, the recovery of the propane carried along withthe residue, which is an essential condition for the economic efficiency of the process, was subject, up to now, to serious technological difficulties.

It has been contemplated, for example, to proceed to a flash followed with a steam stripping. However such a solution was found inoperative since, on the one hand, the foaming tendency of the residue resulted in a substantially immediate clogging of the stripping colurnn while, on the other hand, the recovered propane due to the same foaming tendency, still contains a high .amount of residue, the subsequent deposit of which on the surface of the propane condensers exchangers with indirect contact). has always been an obstacle to a satisfactory operation of said exchangers.

One of the objects of the present invention consists of carrying out the separation of the paraffinic hydrocarbon from the residue while avoiding the abovementioned drawbacks.

Another object of this invention consists of reducing the operating cost resulting in particular from the heating and the compression of the products.

Other objects will appear'from the following description given with reference to the accompanying drawing.

Used oil is introduced through line 1 into the contact column 3 after admixture with a light paraffinic hydrocarbon, for example propane, fed through line 2.

The oil has been optionally pretreated, for example, heated under vacuum (pretreatment not shown in the drawing). The light paraffinic hydrocarbon or solvent will be considered, in the following description, for sake of simplification, as being propane; it must be understood however that the invention is not to be limited to this particular case. The temperature and pressure conditions prevailing in the column are variable but generally close to the critical values of the paraffinic hydrocarbon; for example the temperature will be between and C and the pressure between 25 and 50 kglcm At the lower part of the column, there is withdrawn, through line 4, a sludge or viscous residue containing impurities,essentially of the asphaltene type, said residue carying along a part of the propane therewith.

At the upper part of the column, there is recovered, through line 5, a mixture of clarified oil and propane which, after passage through the valve 6 and after admixture with the hot liquid from line 7 (the origin of which will be stated hereinafter), is conveyed to a first flash zone 8.

In said zone there is achieved a first separation between the clarified oil and the propane vapors, the latter being withdrawn through line 9. These vapors are obviously at a pressure lower than that prevailing in column 3, for example at a pressure between 5 and 25 kg/cm and, more generally, from 10 to 20 kg/cm the temperature of the mixture introduced into the flash zone 8 being generally from about to about 250C. These values are given only by way of illustration.

The liquid product, consisting essentially of oil still containing propane is withdrawn through line l0,'then heated in the oven 11, for example to a temperature of about -350C. A part of the product issued from the oven through line 12 is conveyed, through line 7, to the inlet of the flash zone 8 and has the effect of heating the mixture from line 5.

The other part is conveyed, by 'line' 13, through the valve 14, to a second flash zone 15. 7

There is finally obtained in line 16 a clarified oil substantially free of propane. This oil may be subjected to finishing treatments, for example a treatment with sulfuric acid, followed with a treatment with earth completed with adistillation, itself followed by a treatment with earth of the purified oil cuts thus obtained. In said second flash zone 15, there are further obtained propane vapors which, after condensation and recycling of the oil vapors carried along therewith, if any, are conveyed through line 17, to a compressor 18. The propane vapors, issuingfrom said second flash zone are generally at a pressure of about 0.9 to 3 kg/cm.

It has been already stated that, at the base of the column 3 for contacting the used oil with the solvent (for example propane), there is withdrawn a residue still containing solvent which is intended to be recovered in a substantially complete and economical manner, according to this invention.

100C will be about 50 to 0.5 centistokes. This liquid will be, for example, a hydrocarbon cut of the fuel oil type. Generally the volume ratio between the viscosity lowering agent and the residue will be from about 0.2 to about 5 and more particularly from 0.5 to 3.

The viscosity lowering agent is introduced through line 19. The mixture of the residue with thefviscosity lowering agent, flowing through line 20, is first expanded by passage through the valve 32, and then reheated in a reheater (not shown on the drawing), it is finally introduced into a first flash zone for the residue 21, from where there are obtained, through line 22, propane vapors at a pressure substantially equal to that prevailing in line 9, for example a pressure of about kg/cm The remaining liquid product issued from zone 21 is, afterv passage through line 23 equipped with the valve 24, conveyed to a second flash zone 25 of the residue.

From said zone 25, there are again recovered propane vapors through line 26 under a pressure close to that prevailing in line 17 (second solvent recovery from the clarified oil), for example the mixture under a pressure close to 1 kg/cm The mixture of vapors from lines 17 and 26 is compressed in 18 up to a pressure substantially equal to that prevailing in the first flash zones, i .e., from 5 to 25 kg/cm for example a pressure of about 15 kg/cm.

Finally the residue, completely free from solvent, is recovered through line 27. This residue may have a valuable use, for example by combustion, preferably in admixture with the acid sludges obtained during the finishing step of the regenerated oil. As already stated, the vapors issued from the second flash zones (zones 15 and 25) are compressed in 18 up to a pressure equal to that prevailing in said first flash zones. The compressed vapors are admixed with those of line 9, then conveyed through line 28 to an indirect heat exchanger 29 at the outlet of which nearly all the solvent ofline 30 is in the liquid state. In the exchanger 29 there can be used any cooling fluid, for example water.

The liquid circulating through line 30 is then admixed with the vapors from line 22, issued from the first flash zone of the residue 21.

By this contact, the vapors are themselves condensed and the resulting liquid mixture is recovered in the drum 31.

From'this drum, line 2 is provided for recycling liquid solvent to the contact column 3, generally through a pump with one or more stages (not shown in the drawing). It is thus apparent from this drawing, that the solvent vapors obtained by pressure release of the residue in the first flash zone (line 22) do not flow through the cooler exchanger 29 of the indirect contact type, but are condensed by thermal exchange and direct contact with at least one part of the condensed vapors from the other flash zones which, on the contrary, have been condensed by indirect thermal exchange (exchanger 29).

In this way, the clogging of exchanger 29 by the impurities carried along with the vapors circulating through line 22, is then avoided.

These impurities can be deposited in drum 31, but this is not objectionable since this drum, in contrast to exchanger 29, is periodically purged without stopping the operation of the unit. The stream of vapors circulating through line 26 and coming from the second flash zone of the residue is generally low as compared to the i first stream. In addition, it generally contains no residue or only a very small amount thereof. The residue carried along therewith, if any, can be easily stopped at 4 an intermediate cooling stage of the propane compressor (l8) (cooling stage not shown). In view of its relatively small design capacity, this element can be substantially oversized in order to prevent any clogging, without being detrimental to the overall economy of the unit.

What we claim as this invention is 1. In a process for regenerating a used lubricating oil comprising the steps of:

a. contacting said used oil with a liquid solvent selected from the group consisting of propane, butane, pentane and mixtures thereof;

b. separating contacted oil and solvent into:

i. a mixture of clarified oil and solvent, and ii. a viscous residue containing solvent; and

c. fractionating said viscous residue to remove solvent therefrom, wherein the improvement comprises admixing to said viscous residue prior to said fractionating a viscosity lowering agent, said agent being a hydrocarbon cut having a viscosity of 0.5-50 centistokes at C, whereby foaming and clogging of downstream fractionating equipment is reduced.

2. A process as defined by claim 1 wherein the volumetric ratio of viscosity lowering agent to residue is 0.2:1 to 5:1.

3. A process as defined by claim 1 wherein the volumetric ratio of viscosity lowering agent to residue is 0.521 to 3:1.

4. In a process for regenerating a used lubricating oil comprising the steps of:

a. contacting said oil with a liquid solvent selected from the group consisting of propane, butane, pentane and mixtures thereof;

b. separating resultant contacted oil and solvent into:

i. a mixture of clarified oil and solvent, and ii. a viscous residue containing solvent c. fractionating said mixture of clarified oil and solvent to form separated solvent vapor, and

d. fractionating said viscous residue containing solvent to form separated solvent vapor containing entrained impurities, the improvement which comprises condensing said solvent vapor separated from said clarified oil in indirect heat exchange relationship with a coolant in a condenser, and employing resultant condensed solvent to condense by direct heat exchange contact said solvent vapor containing condensed impurities, whereby said entrained impurities are not deposited on heat exchange surfaces of acondenser.

5. A process as defined by claim 4, further comprising admixing to said viscous residue prior to said fractionating a viscosity lowering agent, said agent being a hydrocarbon out having a viscosity of 0.5-50 centistokes at 100C, whereby foaming and clogging of downstream fractionating equipment is reduced.

6. A process for regenerating used lubricating oils comprising contacting the used oils with a light liquid paraffinic hydrocarbon solvent; separating resulting contact mixture into a mixture of (a) clarified oil and solvent and (b) a viscous residue carrying along part of the solvent therewith, subjecting said mixture of (a) clarified oil andsolvent to a first pressure release and a first step of distillation of the solvent contained therein under a first pressure of 5-25 kg/cm, then to a second pressure release and a second step of distillation of the solvent contained therein under a second pressure of 0.9-3 kg/cm; and admixing to said (b) viscous residue carrying along a part of the solvent, with a hydrocarbon cut having a viscosity of 05-50 centistokes at 100C, and subjecting the resulting mixture of residue and hydrocarbon cut to a pressure release and a distillation of the solvent carried along therewith, wherein the latter distillation is conducted in two successive stages, a first stage at 5-25 kg/cm and a second stage at 0.9-3 kg/cm.

7. A process according to claim 6, wherein both streams of solvent vapors obtained from the two pressure release and distillation of the mixture clarified oilsolvent and the stream of solvent vapors issued from the second pressure release of the residue are admixed with each other and condensed by indirect heat exchange with a coolant before being, at least partly, contacted directly with the stream of the solvent vapors issued from the first pressure release of the residue, this direct contact resulting in the condensation of the vapors issuing from said first pressure release of the residue.

8. A process according to claim 6, wherein the stream of vapors from the second pressure release of the mixture (a) of clarified oil and solvent is preliminarily admixed to the stream of vapors from the second pressure release of the residue and the whole mixture is compressed before being admixed with the stream of vapors from the first pressure release of the mixture of clarified oil and solvent.

9. A process according to claim 6, wherein the hydrocarbon cut is used in a proportion of 0.2 to 5 parts by volume per part by volume of the viscous residue.

10. A process according to claim 6, wherein the first step of distillation of the mixture (a) of clarified oil and solvent and the first step of distillation of the solvent from'the mixture of residue and hydrocarbon cut are conducted under a pressure between l0 and 20 kg/cm 11. A process according to claim 6, wherein the hydrocarbon cut is a fuel oil cut. 

2. A process as defined by claim 1 wherein the volumetric ratio of viscosity lowering agent to residue is 0.2:1 to 5:1.
 3. A process as defined by claim 1 wherein the volumetric ratio of viscosity lowering agent to residue is 0.5:1 to 3:1.
 4. In a process for regenerating a used lubricating oil comprising the steps of: a. contacting said oil with a liquid solvent selected from the group consisting of propane, butane, pentane and mixtures thereof; b. separating resultant contacted oil and solvent into: i. a mixture of clarified oil and solvent, and ii. a viscous residue containing solvent c. fractionating said mixture of clarified oil and solvent to form separated solvent vapor, and d. fractionating said viscous residue containing solvent to form separated solvent vapor containing entrained impurities, the improvement which comprises condensing said solvent vapor separated from said clarified oil in indirect heat exchange relationship with a coolant in a condenser, and employing resultant condensed solvent to condense by direct heat exchange contact said solvent vapor containing condensed impurities, whereby said entrained impurities are not deposited on heat exchange surfaces of a condenser.
 5. A process as defined by claim 4, further comprising admixing to said viscous residue prior to said fractionating a viscosity lowering agent, said agent being a hydrocarbon cut having a viscosity of 0.5-50 centistokes at 100*C, whereby foaming and clogging of downstream fractionating equipment is reduced.
 6. A process for regenerating used lubricating oils comprising contacting the used oils with a light liquid paraffinic hydrocarbon solvent; separating resulting contact mixture into a mixture of (a) clarified oil and solvent and (b) a viscous residue carrying along part of the solvent therewith, subjecting said mixture of (a) clarified oil and solvent to a first pressure release and a first step of distillation of the solvent contained therein under a first pressure of 5-25 kg/cm2, then to a second pressure release and a second step of distillation of the solvent contained therein under a second pressure of 0.9-3 kg/cm2; and admixing to said (b) viscous residue carrying along a part of the solvent, with a hydrocarbon cut having a viscosity of 0.5-50 centistokes at 100*C, and subjecting the resulting mixture of residue and hydrocarbon cut to a pressure release and a distillation of the solvent carried along therewith, wherein the latter distillation is conducted in two successive stages, a first stage at 5-25 kg/cm2 and a second stage at 0.9-3 kg/cm2.
 7. A process according to claim 6, wherein both streams of solvent vapors obtained from the two pressure release and distillation of the mixture clarified oil-solvent and the stream of solvent vapors issued from the second pressure release of the residue are admixed with each other and condensed by indirect heat exchange with a coolant before being, at least partly, contacted directly with the stream of the solvent vapors issued from the first pressUre release of the residue, this direct contact resulting in the condensation of the vapors issuing from said first pressure release of the residue.
 8. A process according to claim 6, wherein the stream of vapors from the second pressure release of the mixture (a) of clarified oil and solvent is preliminarily admixed to the stream of vapors from the second pressure release of the residue and the whole mixture is compressed before being admixed with the stream of vapors from the first pressure release of the mixture of clarified oil and solvent.
 9. A process according to claim 6, wherein the hydrocarbon cut is used in a proportion of 0.2 to 5 parts by volume per part by volume of the viscous residue.
 10. A process according to claim 6, wherein the first step of distillation of the mixture (a) of clarified oil and solvent and the first step of distillation of the solvent from the mixture of residue and hydrocarbon cut are conducted under a pressure between 10 and 20 kg/cm2.
 11. A process according to claim 6, wherein the hydrocarbon cut is a fuel oil cut. 